L.A. Philharmonic concerned about potential subway noise

By By Mike Boehm

May 17, 2013 | 6:12 AM

Nothing in the Los Angeles Philharmonic's repertoire calls for 135-ton trains. The orchestra aims to keep it that way when Metro light rail cars start rumbling through a subway tunnel near Walt Disney Concert Hall.

Experts who know the hall's acoustics are worried that the listening experience in the main auditorium could suffer when subway trains begin running 125 feet below the parking garage in 2020.

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"It would be a disaster for Disney Hall," said its architect, Frank Gehry.

Subway planners have assured that noise won't be a problem, but a recent simulation conducted by the Los Angeles County Metropolitan Transportation Authority raised concerns.

The acoustic experiment was conducted April 23 in Thayer Hall, a below-ground performance and recording space at the Colburn School. The intimate venue, near 2nd Street and Grand Avenue, is closer than Disney Hall to the $1.37-billion subway's route, which will include a stretch beneath 2nd Street from Hope Street to Central Avenue.

"They played a solo piano piece through a loudspeaker and had subwoofers that simulated a passing train," said Fred Vogler, a recording engineer who oversees recording sessions and concert-taping for the Colburn School and the L.A. Philharmonic. "The test was several minutes long. Then they said, 'Is anybody troubled by the train sounds?' We said, 'Well, we heard them, if that's what you're asking.' It set off a lot of concerns."

Gehry heard about the test from Vogler, then passed along his concerns to Los Angeles County Board of Supervisors member Zev Yaroslavsky and others. He said projections of subway noise done nearly two years ago by Metro's noise abatement consultants, who predicted there would be no audible impact on Disney Hall, should be reviewed.

"The flag is up, and we should go over it and make sure," the architect said.

Art Leahy, Metro's chief executive, said that the simulation didn't represent the actual expected sonic impact of the trains. He said it was part of the process of determining just how exacting the noise abatement devices along the tracks must be to meet Metro's goal, which is no additional noise at all in performance spaces near the subway. In addition to noise-abatement consultants, Metro has hired an acoustics expert.

"We are not about to do anything which in any fashion, however slightly, impairs or damages … Disney Hall or any other feature in that area," Leahy said. "They are critically important, and we are simply not going to build something that reduces the utility or benefit of those facilities. That's a blanket statement, no conditions or qualifiers on it."

The standard to be met isn't just preventing noise that an audience can hear, Leahy said, but the more stringent one of eliminating sounds that a recording microphone can pick up.

Yaroslavsky and Stephen Rountree, president of Disney Hall's landlord, the Music Center, said they will arrange a meeting in which cultural organizations adjacent to the subway route, which include the upcoming Broad Collection contemporary art museum and REDCAT, can receive an update from Metro project officials.

Rountree said the Music Center is retaining Disney Hall's acoustical designer, Yasuhisa Toyota, and its original noise abatement engineer, Charles M. Salter Associates, to go over Metro's noise projections, which raised no concerns when presented to cultural leaders in fall 2011.

"If new information has come up, we want to make sure it is reassessed and taken into account," Rountree said. "We'll bring in the engineers and go through the numbers one more time and make sure everyone is comfortable."

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The sound simulation at Colburn was aimed at establishing the threshold at which subway noise ceases to be a problem, said Metro's Bryan Pennington, executive officer for the Regional Connector Transit Corridor Project, which will lay 1.9 miles of underground track to connect the Blue Line and Expo Line with the Gold Line.

The testing will help Metro set the maximum allowable decibel level for each performance space, which the subway's eventual design and construction contractors will have to satisfy.

Pennington said a June simulation at Thayer Hall will be at 36 decibels, down from 39 decibels in April. Lowering a sound by 10 decibels makes it seem half as loud. He expects construction to begin at 2nd and Grand in two to three years. The project depends largely on federal funding that Metro hopes to land by the end of 2013.

The Environmental Impact Report, approved by the Metro board in January 2012, calls for common noise abatement features that reduce vibrations from passing trains, including rubber cushioning beneath the tracks, and rubberized fasteners to hold them in place. The result, it predicts, will be no audible impact on the nearby performance spaces.

The measured ambient noise level inside Disney Hall — the sound when nothing is happening — ranged from 24 to 28 decibels, according to the environmental report. It said Federal Transportation Authority noise standards call for a transit impact on concert halls of no more than 25 decibels— and that abatement measures will ensure that two passing trains project just 16 decibels into Disney Hall.

Pennington said that setting a speed limit lower than the 15 mph anticipated near Disney Hall also would reduce noise, but he doesn't expect that will be necessary.

Metro already has met the challenge of protecting recording studios in Hollywood from noise along its Red Line subway, he noted, even though the rail cars are heavier, and their vibrations bigger, than the ones that will run near Disney Hall.

Toyota, Disney Hall's acoustical designer, said that that the foundations of subway-adjacent performance halls he worked on in Tokyo and Shanghai have special features that reduce ground vibrations, but not Disney Hall. Widely acclaimed for its superior sound since opening in 2003, Gehry's space and Toyota's acoustics provided a platform for the Los Angeles Philharmonic to attract superstar conductor Gustavo Dudamel as its music director.

"We didn't assume a big vibration, such as from a subway, was going to come," Toyota said, and there's nothing further that can be done to the building now.

Deborah Borda, president of the philharmonic, said she isn't alarmed by the recent Colburn School noise simulation but thinks it's helpful that it has brought increased awareness.

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"I think it's a good thing that there's a certain amount of uproar.... I have a comfort level with the [planning] process to this point, but the process is not completed," she said. "We all agree more analysis is required. [Disney Hall] is a treasure that has to be protected and maintained, and it will be."

Colburn School's president, Sel Kardan, issued a statement saying "we are working in a positive way" with Metro officials to keep its music facilities free from subway noise.

Yaroslavksy, a classical music buff, said the task now is "to determine whether the 2011 studies are valid or something slipped through the cracks. I'm not going to prejudge it or get hysterical about it. Obviously Metro will not build a line that is going to compromise Disney Hall."

Until reports of the Colburn School simulation began to circulate, "everybody was in sync" about the subway not being a noise threat, Yaroslavsky said. "If they're not in sync now, we'll get to the bottom of it. We want to find out what the facts are, and if the truth is that vibrations may compromise the acoustics of Disney Hall, Metro is going to have to adjust accordingly."